FIG. 1A is a diagram schematically showing the structure of a tail pipe section of a conventional combustor seen from an exhaust side of burning gas. Also, FIG. 1B is sectional views showing sections of the tail pipe section of the conventional combustor along the lines A-A and B-B shown in FIG. 1A. As shown in FIG. 1A, when a plurality of combustors are annularly provided with around one axis, an upper flange 1a and a lower flange 1b are provided for an end portion of a main body 3 of the tail pipe section to fix an upper seal section 10a and a lower seal section 10b so that the burning gas can be prevented from leaking from a gap between adjacent tail pipes. Also, a gusset 4 is provided for an upper portion of the main body 3 of the tail pipe section to fix the main body 3 of the tail pipe on the housing of the gas turbine. Also, side seals 2a and 2b are provided for the side walls of the main body 3 of the combustor tail pipe section to function as a partition of the adjacent combustors. As shown in FIG. 1B, the upper seal section 10a and the lower seal section 10b are engaged with the upper flange 1a and the lower flange 1b in the main body 3 of the combustor tail pipe section, respectively. A positioning pin 5a is inserted in an engaging portion of the upper flange 1a of the main body 3 of the combustor tail pipe section and the upper seal section 10a to fix a relative position of them. In the same way, a positioning pin 5b is inserted in an engaging portion of the lower flange 1b of the main body 3 of the combustor tail pipe section and the lower seal section 10b to fix a relative position of them. In this way, the seal sections 10a and 10b are connected with the end portion of the main body 3 of the tail pipe section and the leakage of burning gas from the gaps between the end portion of the main body 3 of the combustor tail pipe section and the seal sections is prevented.
In the conventional gas turbine combustor, there is a case that defects such as thermal deformation is caused due to low cycle fatigue in the end portion (outlet) of the combustor tail pipe section during a burning operation. Since the thicknesses of structural plates are different between the side walls and the upper and lower walls in the end portion of the combustor tail pipe section so that the stiffness of the plate in the upper and lower walls thicker than the side walls is high, the low cycle fatigue is caused when thermal stress is impressed on the end portion of the combustor tail pipe section so that compulsory thermal deformation is caused in a plate of the side wall while a start and a stop of the operation of the gas turbine combustor are repeated. Therefore, while the gas turbine combustor repeats the start and the stop, the metal fatigue due to the thermal deformation is accumulated and a warp is generated in the plate of the side wall to form crack.
FIG. 2 is a diagram showing deformation of the side, upper and lower plates of the end portion of the tail pipe section in the operation of the conventional gas turbine combustor as a specific instance. A temperature is high on the side of inner wall and is low on the side of the outer wall, of the end portion of the tail pipe through which the burning gas passes in the operation of the gas turbine. Therefore, the side, upper and lower plates of the end portion of the tail pipe section are likely to be deformed to be convex in an inner direction. However, the stiffness of the upper flange 1a and lower flange 1b is remarkably high compared with that of side plates of the side walls 2a and 2b. Thus, the side plates in the end portion of the tail pipe section are compulsorily deformed in a direction opposite to a direction of original deformation. Therefore, while strong thermal stress generated in the side plates in the end portion of the tail pipe section, and the metal fatigue is accumulated in the side plates in the end portion of the tail pipe section while the gas turbine combustor repeats the start and the stop. Thus, the defect which is based on the metal fatigue in the side wall is caused.
In conjunction with “Combustor and Gas Turbine” is disclosed in the Japanese Laid Open Patent Application (JP-P2004-84601A). In this conventional example, air compressed by a compressor and fuel are mixed and burned. Generated burning gas is introduced into a turbine through a burning pipe. In such a combustor, an air flow path is provided to extend along a surface of a sidewall section in the sidewall section for the burning pipe. An inlet of the air flow path is provided on a surface of the outer wall of the sidewall section. An outlet of the air flow path is provided for an end surface of the burning pipe.
Also, “Combustor and Gas Turbine” is disclosed in Japanese Laid Open Patent Application (JP-P2003-322337A). In this conventional example, air compressed by a compressor and fuel are mixed and burned. Generated burning gas is introduced into a turbine through a burning pipe. In such a combustor, reinforcement ribs are provided over whole width of a side surface of the burning pipe of an almost rectangular section.
Also, “Gas Turbine Combustor” is disclosed in Japanese Laid Open Patent Application (JP-P2003-193866A). In this conventional example, adjacent transition pieces (tail pipes) in neighborhood of the gas turbine combustor, and a transition piece and an initial stage still wing are engaged through the seal section. In such a gas turbine combustor, a seal section is made of cobalt alloy having a fatigue resistance coating layer, in which a film of carbide or nitride is formed as a lower layer and an alumina film is used as the uppermost surface film. A protection plate of cobalt alloy which contains chrome 15 to 35 weight % and carbon 0.7 to 1.5 weight % for a contact section of the transition piece with the seal section in the engaging portion.
Also, “Gas Turbine Combustor” is disclosed in Japanese Laid Open Patent Application (JP-P2003-185140A). In this conventional example, a combustor transition piece (tail pipe) and an initial stage stillness wing in the gas turbine for power generation are engaged through a seal section. In such a gas turbine combustor, cobalt alloy which contains chrome of 15 to 30 weight % and carbon of 0.05 to 0.25 weight % as a part of the chemical composition is used as a base member. A plate to which a coating of chrome carbide of 0.1 to 0.6 mm as a main component is carried out is used as a seal section. A cobalt alloy plate is attached to a contact section of the seal section with coating layer in the transition engaging portion.